The United Nations, the United States, and other donor nations say they aim to raise more than $2 billion this week for war-torn Iraq during a pledging conference in Washington.

The Iraq donor meeting of 24 countries is being co-hosted by the United States, Canada, Germany, Japan, Kuwait, and the Netherlands, and the main pledge session is scheduled for July 20.

A broader meeting on the U.S.-led campaign to fight Islamic State (IS) militants in Iraq will be held on July 21, to be attended by dozens of defense and foreign ministers from countries in the anti-IS coalition.

Iraq has a humanitarian crisis of large proportions, with an estimated 3.3 million people displaced by the war with IS.

Both Germany, Iraq's largest donor, and Canada came forward with pledges of additional aid of $1.3 million and $121 million, respectively, on July 19.

"We cannot lose the momentum of our efforts to stabilize Iraq now," German Foreign Minister Frank-Walter Steinmeier said on July 20 ahead of the Washington conference.

"When the city of Mosul is freed from Islamic State, we will face enormous humanitarian, societal, and political challenges, just as we saw when Fallujah was liberated," he said.

Iraqi Prime Minister Haidar al-Abadi has pledged to retake Mosul, Iraq's second-largest city and IS's most important stronghold in Iraq, by the end of the year.

The UN said on July 19 that it needs to raise $284 million in aid to prepare for humanitarian needs from an expected assault on Mosul, and an additional $1.8 billion would be needed to deal with the aftermath.

Besides raising fresh funds to help Iraqi communities get back on their feet once their towns have been recaptured from IS, the aid is to be used to assist with the clearing of unexploded munitions preventing people from returning home, a U.S. State Department official said.

The United Nations has estimated that Iraq needs a total of $4.5 billion in humanitarian assistance. That is far more than the $778 million that is currently set by the UN humanitarian response plan for Iraq.